Abstract
Here we investigate the ocean-atmosphere coupling and the contribution of the Sea Surface Temperature (SST) variations in: 1) Brazil-Malvinas Confluence (BMC) region, 2) Southwest Atlantic Ocean and 3) Southern Brazil. Numerical simulations of the ECHAM5/MPI-OM coupled ocean-atmosphere model were used to analyze the changes in the seasonal trajectory of the extratropical cyclones, in terms of intensification of physical mechanisms and implications for future scenarios. The numerical experiment for the future scenario considered an atmospheric CO2 concentration of approximately 770 ppm, which represents an increment of more than 350 ppm over the current values recorded by the Mauna Loa reference station. For this scenario, the results indicated a Storm Tracks (ST) displacement of 5° latitude toward south and changes of the meridional transport of sensible heat, close to 50°S. The increase in SST induces ST intensification and consequently an increase in the occurrence of extratropical cyclones. Overall, in the BMC region, we found a change in the pattern of cyclogenetic activity occurrence, with less frequent, but more intense events. On the Southern Brazilian region, the results of this study indicate increases in rainfall during summer months, whereas, a decrease in frequency and an increase in intensity were found for wintertime. We suggest that these changes could impact the climate dynamic of the Brazilian South coast, with a magnitude yet unknown.
Highlights
Storm Tracks (ST) in the Southern Hemisphere play a key role in both weather and climate, between middle and high latitude through their latitudinal transports, resulting in a significant impact in society, especially in coast regions [1] [2] [3]
Reduction in Kinetic Energy (KE) values in Global Warming (GW) scenario takes place during DJF, which may affect the climatic conditions of the south coast of South America
For JJA, we found a decrease in KE magnitude associated with a decrease in synoptic systems (BMC region) due to displacement of ST to South
Summary
Storm Tracks (ST) in the Southern Hemisphere play a key role in both weather and climate, between middle and high latitude through their latitudinal transports, resulting in a significant impact in society, especially in coast regions [1] [2] [3]. The primary effects of ST mobile in climate include changes in cloudiness, energy balance and sea level. They have a significant influence in the atmospheric general circulation [1] [5] [6]. According to [7], the eastern coast of South America is a region that is favorable for the occurrence of cyclogenesis, with a well know seasonal pattern of formation and intensification. The authors suggested that the temperature contrast between the continent and the ocean, associated with the sea surface temperature (SST) gradient of the Brazil-Malvinas Confluence region (BMC), leads to conditions that intensify latent and sensible fluxes; these, in turn, are important for the development of extratropical cyclones
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